What happened April 1809 AD

In the early morning of 10 April, leading elements of the Austrian army crossed the Inn River and invaded Bavaria.

Napoleon arrived at Donauwörth on 17 April to find the Grande Armée in a dangerous position, with its two wings separated by 120 km (75 mi) and joined together by a thin cordon of Bavarian troops. Charles pressed the left wing of the French army and hurled his men towards the III Corps of Marshal Davout. In response, Napoleon came up with a plan to cut off the Austrians in the celebrated Landshut Maneuver.

Napoleon realigned the axis of his army and marched his soldiers towards the town of Eckmühl. The French scored a convincing win in the resulting Battle of Eckmühl, forcing Charles to withdraw his forces over the Danube and into Bohemia.